One, a 63-year-old, was held at the Peter Boddy slaughterhouse in Todmorden, West Yorks, which was raided on Tuesday.

The abbatoir is one of five licensed premises in the UK to handle horse carcasses.

Also arrested yesterday was Dafydd Raw-Rees, 64, owner of Farmbox Meats, near Aberystwyth, which was raided on the same day. His processing plant in the Welsh countryside handles horsemeat but Mr Raw-Rees insisted the 14 workers there only cut it up for export.

The third arrest was a 42-year-old man, also at Farmbox Meats.

Dyfed Powys Police said: “They will be interviewed jointly by police and FSA staff in what has become a joint operation.”

The men were held hours after a French food company was accused of knowingly selling horsemeat which ended up on British plates.

Spanghero, based near Toulouse, was accused of “economic fraud” by the French government which said it was “well aware” of their actions.

Spanghero sold Romanian meat to frozen food giant Comigel. It was later sold at supermarkets, including Aldi and Tesco. French minister Benoit Hamon said a “fraudulent trade” had been going on since at least August.

In the UK last night, Asda withdrew its 500g Beef Bolognese Sauce from sale after tests found horse DNA.

It also withdrew three products from the same supplier as a precaution – 600g Beef Broth Soup, 500g Meat Feast Pasta Sauce and 400g Chilli Con Carne Soup.

Meanwhile, the cancer-causing horse painkiller bute has been found in the food chain.

But Britain’s Chief Medical Officer Dame Sally Davies said the risk of harm to humans was virtually “nil” when eaten in horsemeat.

She stressed: “People should not panic. If you ate 100% horse burgers of 250g, you would have to eat, in one day, more than 500 or 600 to get to a human dose.”